Experiment 4 - TanishaBillups Experiment4 February20,2008

Tanisha Billups Experiment 4 February 20, 2008 Colligative Properties: Freezing-Point Depression and Molar Mass Purpose: The purpose of this lab is to apply the colligative property of freezing-point depression and to use it to determine the molar mass of an unknown substance. Procedure A: Cooling Curve for Pure Naphthalene 1. Weight a large test tube to the nearest .01g 2. Add 15 to 20g of naphthalene 3. Weigh the test tube again 4. Insert a thermometer into a 2-hole stopper 5. Loop a wire loosely around the thermometer and extend the straight part of the wire out of the second hole in the stopper (to stir the solution) 6. Make a water bath using a 600-mL beaker that has been placed on a tripod or o-ring (use wire gauze) 7. Fill the 600mL beaker nearly full of water and heat it to 85°C 8.

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